Ovarian carcinoma is the leading cause, of death from gynecologic malignancy, resulting in approximately 21,880 estimated new cases in 2010 with an estimated 13,850 deaths in 2010 in the USA [30]. Most OVCA arises from the ovarian surface epithelium (OSE) [31] and clinically, it often involve the ovary and omentum, with diffuse, multi-focal intraperitoneal metastases and malignant ascites [1]. Metastasis of OVCA (FIG. 1) involves shedding of cells from the primary OVCA either as single cells (SCs) or as spheroids or multicellular aggregate (MCAs) that later interact with mesothelial cells that line the inner surface of the peritoneum and disseminate to adjacent pelvic organs [9, 32, 33]. Most OVCA patients (approximately 75%) are diagnosed too late with disseminated intra-abdominal disease (stage IV) and because of this late diagnosis they have low survival rates [34]. For therapy, patients usually undergo cytoreductive surgery followed by the administration of the standard first line chemotherapeutic combination regimen of carboplatin and paclitaxel [2, 5, 35]. Nevertheless, most of the patients will eventually suffer from therapeutic resistance and undergo relapse of OVCA [35, 36].
Evidence points to the role of inflammation in both ovulation and OVCA [13, 37]. It appears that the inflammation within the peritoneal microenvironment of OVCA contributes to progression of OVCA due to immune cell infiltration into the OVCA microenvironment [13, 14]. It has been reported that in OVCA leukocytes are present within the ascitic fluid including activated macrophages and T cells and to a lower numbers natural killer cells, B cells, and mast cells [14]. These activated immune cells produce reactive oxygen species and secrete cytokines and angiogenic and growth factors that promote OVCA progression [38].
Antibodies, regardless of their source or antigenic specificity, and T cell receptors catalyze the formation of ozone (a molecule with the chemical signature of ozone) through water oxidation in presence of singlet molecular oxygen (FIG. 2) and cause bacterial toxicity [16, 18, 39, 40]. In vivo, this reaction occurs due to activated immune cells which are the source of singlet molecular oxygen[16, 17]. In a tube singlet molecular oxygen is generated by adding a photosensitizer and exposing the tube contents to near UV irradiation, i.e. employing a photochemical source [16, 18]. However in vivo singlet molecular oxygen is known to be generated by activated neutrophils [25, 26]. For example, ozone was formed in vivo in a reversed-passive Arthus reaction generated through intradermal injections in rats using albumin and anti-albumin antibody were ozone was detected in the inflammatory legions [16]. Moreover, Wentworth and coworkers reported that ozone was formed in vivo in atherosclerotic plaques in addition to in vitro atherosclerotic plaques in presence of activated leukocytes with generation of atheronals as products of cholesterol ozonolysis [17]. On the other hand, that study has been under debate as the atheronals detected in it as unique products of cholesterol ozonolysis could also be generated, in addition to ozone, through singlet oxygen[41, 42]. Nevertheless, Wentworth and coworkers re-evaluated samples from their first study and demonstrated that the ratios of obtained products indicate involvement of ozone rather than singlet oxygen in formation of the detected atheronals [43, 44].
Ozone, and products of ozonation are known to cause disruption and lysis of phospholipid bilayers and cells [19-21]. Furthermore, reactive oxygen species and ozone cause photolysis of organic molecules and of phospholipids in lipid bilayers supported on spherical or planar platforms [22-24]. If these bilayers are part of liposomes or are supported on porous spheres, then their disruption will result in leakage of their contents such as chemotherapeutic agents.
To summarize, ovarian cancer (OVCA) is a peritoneal disease as its metastasis and dissemination to other organs takes place through the peritoneal cavity [1]. Thus intraperitoneal (IP) administration of chemotherapeutic agents treats local and disseminated OVCA as it is confined to the peritoneum. Recently the efficacy of IP chemotherapy of OVCA has been demonstrated when done alone or in combination with intravenous chemotherapy [2-5]. This is probably due to direct delivery of drugs to several types of peritoneal OVCA cells that play a role in chemotherapeutic resistance such as cancer stem cells and spheroids [6-12].
The peritoneal microenvironment of OVCA is an inflammatory one due to the infiltration of immune cells that produce reactive oxygen species and secrete factors that promote tumor progression [13, 14]. Recent reports demonstrated that ozone is generated in vivo in inflammatory diseases [15-17]. This production of ozone is the direct outcome of an antibody's oxidative catalytic activity [16, 18]. Antibodies, regardless of their source or antigenic specificity, catalyze the generation of ozone and peroxide by a water oxidation pathway [16, 18]. The only requirement for antibodies to mediate this reaction is a source of singlet molecular oxygen, which is provided in vitro by near UV irradiation in presence of a photosensitizer [16, 18]. In vivo, the only requirement for this reaction to occur is the presence of activated immune cells which are the source of singlet molecular oxygen in addition to mediating the water oxidation pathway and generating ozone [16, 17].
Ozone and other ROS are known to cause peroxidation of phospholipid bilayers and formation of free radicals resulting in lysis of lipid bilayers made of phospholipids [19-24]. If these bilayers are part of liposomes or are supported on porous nanospheres, then their disruption by ROS results in leakage of their contents such as chemotherapeutic agents.
Thus, the need exists for a nanocarrier for IP therapy of OVCA that can (1) utilize generation of ROS mediated by activated immune cells in inflammatory diseases like OVCA [16, 17, 25, 26]; (2) enable ROS to disrupt lipid bilayers whether free or supported on spherical or planar platforms [19-24]; and (3) use robust supported lipid bilayer membrane assemblies on porous nanoparticles that have capabilities to entrap chemotherapeutic agents [27-29].